1. Field of the Invention
This invention relates to a slide gate mechanism for a container employed to hold molten metal. More specially, this invention relates to such a slide gate mechanism comprising refractory bodies which have been impregnated with carbon containing media, especially, in accordance with the invention, an oil containing less than 10% by weight pitch.
2. Discussion of the Prior Art
Slide gate mechanisms for use in connection with vessels containing molten metal are heretofore known and have been used in the Steel Industry in ladles and the like. These slide gates are composed of a metallic housing or framework and refractory bodies. The refractory bodies which come in direct contact with molten metal contained within the container consist essentially of a head (top) plate, stationary arranged in the metallic housing, and a slide plate (slide gate) with a collector nozzle slideable in said metallic housing against said head plate. The slide gate mechanism itself has proved itself useful in steel casting, in particular, in vacuum treatment and continuous casting.
The requirements for the refractory bodies of the slide gate have increased owing to increases in the size of ladles employed and a lengthening of the casting times. It is obvious that the head and slide plate which come in contact with the molten metal can undergo some degradation owing to the high temperatures at which it is employed. It is particularly desirable to provide plates which can be used repeatedly i.e., which are resistant to the aggressive influences of the molten metal to which they come in contact.
It has been proposed to provide plates with a carbon-containing material. Thus, it has already been proposed to impregnate converter bricks, torpedo ladle bricks, blast furnace bricks, or the like with some carbon-containing material whereby the pore volume of the body made of the refractory material (said pore volume being about 15% by volume of the body) contain tar containing 60 to 90% by weight pitch. The use of this high pitch containing tar leads to a carbon content of the refractory bodies (brick) of about 5% by weight. It has been suggested that this high carbon content prevents infiltration of slags and steel and thereby decreases the rate of degradation and abrasion of the plates.
The aforesaid described procedure has also been used for the refractory bodies of slide gates. Thus, according to German Offenlegungsschrift No. 2,107,127 it has been proposed to impregnate the plates of magnesite with carbon-containing material. The following positive influences on the abrasion behaviour are substantially attributed to this tar impregnation:
1. Reduction in slag and steel infiltration. PA1 2. Improvement in the locking and sliding behaviour by surface evaporating tar components. PA1 3. Improvement in the resistance to sudden changes in temperature of the ceramic material.
However, according to this technique, considerable tar quantities evaporate upon use at the ladle and condensation of the same occurs in the slider housing on springs, cooling channels and upon other mechanical parts. Hence, it has become necessary to remove the slide gate after only a few castings and to thoroughly cleanse the same. This removal and cleansing operation entails a considerable amount of work with possible lowering of production.
It has also heretofore been proposed to subject the plates to a temperature treatment between 300.degree. and 600.degree. C. before the same are used in order to avoid the evaporation of tar upon use of the slide gate and the deposition of quantities of condensated material upon the mechanical parts. The high initial tar discharge is avoided vis-a-vis the non-tempered impregnated plates. However, by such a thermal treatment the life of the slide gates themselves is reduced.
Accordingly, it is an object of the present invention to provide refractory bodies for a slide gate mechanism characterized by a long working life and a low degree of contamination of related mechanical parts upon use. It is a particularly desirable object of the present invention to provide a slide mechanism for a sliding gate which can be repeatedly used without contamination of mechanical parts and substantial impairment of their mechanical features owing to deposition of tar and the like thereon.